On the original topic: I recall a run of Marvel's 1990s what If? series where the Watcher and some other folks were recruiting versions of the Fantastic Four from various What If? universes. They had to defeat Kang (I think), who had achieved ultimate power. As I recall, they just kept on sending FF team after FF team against Kang, who kept blowing them away. I don't remember if any of them teamed up with each other, though.
In the end
One wonders why nobody thought of this a little sooner.